Method and arrangement for influencing light propagation directions

Abstract

A method for influencing light propagation directions of a plurality of illuminated surfaces, comprising: arranging switchable absorbers on the light-exit side of the surfaces, such that light only exits through portions of the surfaces which are in front of the surfaces; switching on the absorbers for a first operating state so that a portion of the light emanating from the surfaces is absorbed, while the rest of the light exits at the surface portions of the light-exit side of the surface substrates at which no switchable absorbers are applied, resulting in light only being visible from a limited viewing angle which is defined by the shape of the switchable absorber, the shape of the surface, refractive index conditions in, and thickness of, the substrates of the surfaces; and switching off the absorbers for a second operating state so that light from the surfaces is visible from an unrestricted viewing angle.

The invention claimed is: 
     
       1. A method for influencing light propagation directions of a plurality of adjacent self-luminous and/or illuminated surfaces which comprise a transparent substrate on a light exit side, wherein the substrate is arranged above a layer of the self-luminous or illuminated surfaces which generates light, and wherein, in a first alternative, each surface comprises its own substrate and, in a second alternative, all of the surfaces comprise a common, two-dimensionally extensive substrate, comprising the following steps:
 arranging, for at least a quantity of the surfaces, switchable absorbers in each instance on the light exit side on one or more partial surfaces of the respective substrate in the first alternative or on one or more partial surfaces of the common substrate in the second alternative, wherein a main spatial direction of propagation of the switchable absorbers lies parallel to the light exit surface of the substrate or substrates to within a tolerance of a maximum of 10°, 
 limiting the light propagations of the light emanating from each individual surface in such a way that light of a surface does not exit through the substrate or the portion of a substrate which is located in front of another surface in parallel projection, but only exits through the substrate portion which, in parallel projection, is located exclusively in front of the surface under consideration, 
 switching on the absorbent effect of the switchable absorbers for a first operating state B 1  so that a portion of the light emanating from the surfaces is absorbed, while the rest of the light exits freely at the surface portions of the light exit side of the substrate at which no switchable absorbers are applied, as a result of which the light of the respective relevant surfaces is only visible in each instance from a limited viewing angle which is defined by a geometric shape of the switchable absorber, a geometric shape of the respective surface, refractive index conditions in a setup and thickness of the substrate, 
 switching off the absorbent effect of the switchable absorbers for a second operating state B 2  so that the light emanating from the surfaces, with the exception of residual absorption losses of the switchable absorbers, can propagate freely through same, as a result of which the light of the respective relevant surfaces is visible from an unrestricted viewing angle. 
 
     
     
       2. The method according to  claim 1 , wherein either the switchable absorbers associated with all of the surfaces are switched simultaneously between operating states B 1  and B 2  for a full area switching or in that switching between the operating states B 1  and B 2  is carried out only over a partial area in that only a strict subset of the switchable absorbers is switched. 
     
     
       3. The method according to  claim 1 , wherein the limiting of the light propagations of the light emanating from each individual surface is carried out by arranging permanently or switchably absorbent layers between the individual substrates in the first alternative or inside of the one common substrate in the second alternative, wherein planes in which the switchable absorbers and the absorbent layers are arranged, respectively, and extend perpendicular to one another to within a tolerance of, at most, 25 degrees. 
     
     
       4. The method according to  claim 1 , wherein the limiting of the light propagations of the light emanating from each individual surface is carried out by selecting the refractive index conditions of the substrate relative to air in such a way that unwanted rays are converted into total reflection. 
     
     
       5. The method according to  claim 1 , wherein a collimating lens is arranged on the partial surfaces of the substrates or substrate on which no switchable absorber is applied in order to achieve a further beam focusing. 
     
     
       6. The method according to  claim 1 , wherein every switchable absorber comprises an electrochromic layer and/or a liquid crystal layer and/or an electrophoresis-based layer and/or a layer based on electrowetting with absorbent particles which can be controlled by an electric field. 
     
     
       7. The method according to  claim 1 , wherein every switchable absorber comprises a switchable color filter by which a color spectrum of the color emitted through a surface thereunder is absorbed in a first state and transmitted in a second state, and wherein the switchable color filter can be controlled with respect to its state by an electric field. 
     
     
       8. The method according to  claim 1 , wherein every switchable absorber has a geometry of a pinhole diaphragm or an inverse pinhole diaphragm. 
     
     
       9. The method according to  claim 1 , wherein there is provided a multitude of self-luminous or illuminated surfaces which, in their entirety, form a display screen, so that the display screen can be switched between the operating state B 1  for a limited viewing angle and the operating state B 2  for an unrestricted viewing angle. 
     
     
       10. The method according to  claim 9 , wherein the self-luminous surfaces correspond in each instance to a smallest pixel or a cluster of smallest pixels of an OLED display screen, mini-LED display screen, VCSEL display screen, QLED display screen, LED display screen or micro-LED display screen. 
     
     
       11. The method according to  claim 9 , wherein every switchable absorber has a geometry of a pinhole diaphragm, and the pinhole diaphragms are arranged on the partial surface or the partial surfaces of the common substrate or of the respective substrate such that geometric centroids of the self-luminous or illuminated surfaces and of the surface portions not covered by the switchable absorbers do not coincide with one another in parallel projection at least in some of the surfaces. 
     
     
       12. The method according to  claim 9 , wherein the illuminated surfaces correspond in each instance to a smallest pixel or a cluster of smallest pixels of an LCD display screen. 
     
     
       13. The method according to  claim 1 , wherein every switchable absorber has a geometry of an inverse pinhole diaphragm, and microstructured outcoupling elements which couple the totally internally reflected rays out of the common substrate or respective substrate accompanied by a change in direction are arranged on partial surfaces not covered by the absorbers, and wherein the light coupled out through the microstructured outcoupling elements is only visible from the limited viewing angle. 
     
     
       14. The method according to  claim 1 , wherein permanently scattering microstructures are arranged on the switchable absorbers. 
     
     
       15. The method according to  claim 14 , wherein the scattering microstructures couple out and/or scatter totally internally reflected rays in a substrate. 
     
     
       16. Use of the method of  claim 1  in a planar illumination source comprising self-luminous or illuminated surfaces for backlighting an LCD panel so that the LCD panel can be operated in the first operating state B 1  for a limited viewing angle and in the second operating state B 2  for an unrestricted viewing angle. 
     
     
       17. An arrangement for influencing light propagation directions, comprising:
 a plurality of adjacent self-luminous and/or illuminated surfaces which comprise a transparent substrate on a light exit side, wherein the substrate is arranged above a layer of the self-luminous or illuminated surfaces which generates light, and wherein, in a first alternative, every surface has its own substrate ( 1 ), and, in a second alternative, all of the surfaces comprise a common, two-dimensionally extensive substrate, 
 for at least a quantity of surfaces, switchable absorbers arranged on the light exit side in each instance on one or more partial surfaces of the respective substrate in the first alternative or on one or more partial surfaces of the common substrate in the second alternative, wherein a main spatial direction of propagation of these switchable absorbers lies parallel to the light exit surface of the substrate or substrates to within a tolerance of a maximum of 10°, 
 a light limiter for limiting the light propagations of the light emanating from each individual surface such that light of a surface does not exit through the substrate or the portion of a substrate that is located in front of another surface in parallel projection, but only exits through the substrate portion which, in parallel projection, is located exclusively in front of the surface under consideration, 
 a switch for switching on and switching off the absorbent effect of the switchable absorbers such that: 
 the absorbent effect of the switchable absorbers is switched on for a first operating state B 1  so that a portion of the light emanating from the surfaces is absorbed, while the rest of the light exits freely at the surface portions of the light exit side of the substrate at which no switchable absorbers are applied, so that the light of the respective relevant surfaces is only visible in each instance from a limited viewing angle which is defined in particular by a geometric shape of the switchable absorber, a geometric shape of the respective surface, refractive index conditions in a setup, and a thickness of the substrate, and so that 
 the absorbent effect of the switchable absorbers is switched off for a second operating state B 2  so that the light emanating from the surfaces, with the exception of residual absorption losses of the switchable absorbers can propagate freely through same, as a result of which the light of the respective relevant surfaces is visible from an unrestricted viewing angle. 
 
     
     
       18. A method for influencing the light propagation directions of a plurality of adjacent self-luminous and/or illuminated surfaces which comprise a transparent substrate on the light exit side, wherein the aforementioned substrate is arranged above the light-generating layer of the self-luminous or illuminated surfaces, and wherein, in a first alternative, every surface comprises its own substrate and, in a second alternative, all of the surfaces comprise a common, two-dimensionally extensive substrate, having the following steps:
 arranging, for at least a quantity of surfaces, switchable absorbers on a light exit side on one or more partial surfaces of the respective substrate in the first alternative or on one or more partial surfaces of the common substrate in the second alternative, wherein the main spatial direction of propagation of these switchable absorbers lies parallel to the light exit surface of the substrate or substrates to within a tolerance of a maximum of 10°, and wherein at least two separately switchable absorbers are provided in front of every surface and can be switched, respectively, to transparent and opaque so as to complement one another, 
 limiting the light propagations of the light emanating from each individual surface in such a way that light of a surface does not exit through the substrate or the portion of a substrate which is located in front of another surface in parallel projection, but only exits through the substrate portion which, in parallel projection, is located exclusively in front of the surface under consideration, 
 switching on the absorbent effect of a selection of switchable absorbers and switching on the transparent effect of the selection of switchable absorbers complementing the aforementioned selection of switchable absorbers for an operating state B 5  so that a portion of the light emanating from the surfaces is absorbed, while the rest of the light exits freely at the surface portions of the light exit side of the substrate at which no switchable absorbers are applied or an absorber switched to transparent is applied, as a result of which the light of the respective relevant surfaces is only visible in each instance from a first limited viewing angle which is defined in particular by selection and a geometric shape of the switchable absorbers, a geometric shape of the respective surface, refractive index conditions in a setup, and a thickness of the substrate, 
 switching on the transparent effect of the aforementioned selection of switchable absorbers and switching on the absorbent effect of the selection of switchable absorbers complementing the aforementioned selection of switchable absorbers for an operating state B 6  so that a portion of the light emanating from the surfaces is absorbed, while the rest of the light exits freely at the surface portions of the light exit side of the substrate at which no switchable absorbers are applied or an absorber switched to transparent is applied, so that the light of the respective relevant surfaces is only visible in each instance from a second limited viewing angle which is defined by a selection and a geometric shape of the switchable absorbers, a geometric shape of the respective surface, refractive index conditions in a setup, and a thickness of the substrate, 
 switching operating states B 5  and B 6  one after the other in a cyclically timed manner, and displaying at least two different image contents on the surfaces alternately in the same cyclical timing, 
 so that an autostereoscopic display or a dual view display is achieved on the surfaces depending on the first limited viewing angle and second limited viewing angle and depending on image contents displayed.